System and method for managing usage quotas

ABSTRACT

A system for managing computer resource usage quotas includes a distributed gateway service, a plurality of clients, an internal network, a distributed storage service a system management service, a configuration database, and a distributed metadata service. A method for managing computer resource usage quotas applied to a plurality of users of data includes the steps of defining one or more resource classes, defining at least one usage policy for the resource classes, tracking quota usage for the usage quotas in accordance with the usage policy, and enforcing quota usage for the usage quotas, and storing the data in accord with the resource class definitions. Optionally, the quota usage may be aggregated.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to commonly owned, co-pending U.S.application Ser. No. 09/709,187 entitled “Scalable Storage System” byDavid Raccah et al., filed Nov. 10, 2000; U.S. application Ser. No.09/731,418, entitled “Symmetric Shared Storage System,” by Olaf Manczaket al., filed Dec. 5, 2000; and U.S. application Ser. No. 09/664,677,entitled “File Storage System Having Separation of Components,” byGeorge Feinberg et al., filed Sep. 19, 2000; each commonly owned by thepresent assignee, the contents of each being incorporated herein byreference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to computing systems, and moreparticularly to a method and system that define, track, and enforceresource usage quotas based on classes.

BACKGROUND OF THE INVENTION

Computer network technology has improved the exchange of and access toinformation. As a result, computer use has become pervasive for bothbusiness and personal purposes. With increased use, however, has comethe requirement for enterprise and co-location hosting facilities tostore vast amounts of data. The increased demand for storage presentsseveral challenges to providing a tracking and enforcement system thatmanages resource usage.

In any computing system, including distributed scalable storage systems,resources are not infinite and must be managed. Among the types ofresources that must be managed, are for example and without limitation,storage resources available to system users, bandwidth, and even thenumber of files. Managing resources requires defining, tracking, andenforcing user quotas associated with each resource. For example,conventional quota tracking and enforcement methods for storageresources often define user quotas in physical terms, such as how muchspace a user is allocated in a given file system. Although theseconventional storage quota management methods are useful in somerespects, they fail in others. For example, they do not provide for thedefinition of other characteristics about a storage resource that may beuseful to manage, and they do not track or enforce quotas through theuse of logical groupings, also called classes, which allow for moreflexibility in quota definition, tracking and enforcement.

Using conventional methods to manage storage quotas, the quotas areviewed in terms of physical bytes. However the cost of resources in adistributed computing system and more particularly a distributedscalable storage system is also influenced by a multitude of otherfactors. Therefore, traditional storage quota management methods fail toadequately define, track, and enforce usage quotas and appropriatelyallocate their respective costs.

Thus, there exists in the industry a need to provide an improved quotatracking and enforcement method and system, which apply logicalgroupings, that is, classes, to user quotas. More particularly, theindustry needs a method, which operates in a distributed computingsystem, which uses classes to define usage quotas, track resource usage,and enforce the defined quotas. The method needs to be applicablethroughout the distributed system wherever quotas need to be allocatedfor a system resource, for example and without limitation, storagequotas. In the case of storage quotas, a user may want to use classesbased on quality of service attributes of the system to determine howfile space will be allocated. Classes add a level of abstraction to theconcept of assigning resources to users. Moreover, a specific cost forstoring a file can be associated with each storage class. This means astorage class quota provides information regarding how much storagespace a user is allowed to use, while a storage class identifies thecost associated with the type of space that the user can use.Additionally, the method and system should be flexible enough to allowtracking and enforcement of quotas for system attributes for example andwithout limitation bandwidth and number of files, and not simply thoseattributes that are defined on a per-directory or per-file system basis.

In light of the above, it would be desirable to arrive at an approach toa quota tracking and enforcement system and method that may be used tomonitor and control usage quotas without some or all of the drawbacks toconventional approaches described above.

SUMMARY OF THE INVENTION

Accordingly, it is an advantage of the present invention to provide aquota management system that allows the use of classes to provide highlycustomizable and easy to use resource usage management.

Another advantage of the present invention is to provide a quotamanagement system in variety of process models such as but not limitedto, a single process, multiple processes, or as distributed processes onmultiple machines.

A further advantage of the present invention is to provide a highlyscalable quota management system that can easily be scaled to providefor the expanding needs of customers.

Another advantage of the invention is to provide a quota managementsystem for allowing the definition of classes that are stored in aconfiguration database and can be used for resource management.

Another advantage of the present invention is to provide a quotamanagement system for allowing a tracking mechanism that monitors usagequotas.

Another advantage of the invention is to provide quota usage trackingfor gathering quota usage information for a partition of a file system.

Another advantage of the present invention is to provide a quotamanagement system for allowing an enforcement mechanism for usage quotasbased on classes.

A further advantage of the present invention is to provide a quotamanagement system for allowing the aggregation of the quota informationfor all partitions of a file system.

In view of the foregoing advantages and others, the present inventionprovides a system and method for defining, tracking, and enforcingquotas based on classes. According to the disclosed embodiments, a quotausage system may include a quota usage server function, quota usageupdater function, and a quota usage database that implements trackingand enforcement services. In addition, the disclosed system and methodare scalable. This is in contrast to conventional approaches thatinclude quota tracking and enforcement, but cannot provide class-basedquota management or highly scalable and customizable quota management.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome apparent to those ordinarily skilled in the art upon review ofthe following description of specific embodiments of the invention inconjunction with the accompanying figures, wherein:

FIG. 1 shows a quota usage management system as a part of a metadataservice and a quota aggregation and enforcement process within ascalable storage system;

FIG. 2 is a flow chart of a method for management of resource usagequotas;

FIG. 3 is a diagram of an exemplary assignment of quality of serviceattributes by storage class ID;

FIG. 4 is a flow chart depicting a method for quota usage definition andreporting;

FIG. 5 is a flow chart outlining a method for quota usage tracking basedon storage class;

FIG. 6 is a flow chart showing a method for quota usage aggregation andenforcement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the implementation of certain elements of thepresent invention may be accomplished using software, hardware or anycombination thereof, as would be apparent to those of ordinary skill inthe art, and the figures and examples below are not meant to limit thescope of the present invention. Moreover, where certain elements of thepresent invention can be partially or fully implemented using knowncomponents, only those portions of such known components that arenecessary for an understanding of the present invention will bedescribed, and detailed descriptions of other portions of such knowncomponents will be omitted so as not to obscure the invention. Further,the present invention encompasses present and future known equivalentsto the known components referred to herein by way of illustration. Thepreferred embodiment of the present invention will be described hereinwith reference to an exemplary implementation in a distributed, highlyscalable storage system. However, the present invention is not limitedto this exemplary implementation, but can be practiced in any computingenvironment including a distributed computing environment.

Looking now to FIG. 1, illustrated is an exemplary distributed, highlyscalable storage system 300 incorporating an exemplary quota usagetracking system 10 a-10 n in accordance with the principles of thepresent invention. (In general, “n” is used herein to indicate anindefinite plurality, so that the number “n” when referred to onecomponent does not necessarily equal the number “n” of a differentcomponent. For example, the number of Gateway Service nodes 70 a-70 ndoes not, but may, equal the number of MDS servers 101 a-100 n in FIG.1.) The distributed computing environment includes a plurality ofclients such as an NFS client 61, CIFS client 62, HTTP client 63, FTPclient 64, and SQL client 65 (collectively clients 11) capable ofconnecting to the data network through a load-balancing node 12. Theseapplications are provided for purposes of illustration only, and are notlimiting. Users may connect to the system through the NFS client 61,CIFS client 62, HTTP client 63, FTP client 64, or SQL client 65. Loadbalancing node 12 then connects to one or more Gateway Service nodes 70a-70 n, (collectively distributed gateway service 13) which areconnected to an internal network 14, for example but without limitation,a switched Internet Protocol (IP) based network. Internal network 14includes one or more network services that provide connectivity toseveral distributed scalable services, for example, but withoutlimitation a scalable distributed Metadata Service (MDS) 15, a scalabledistributed Storage Service 16, a scalable System Management Service(SMS) 17, and a scalable distributed Quota Aggregation and EnforcementService 19.

The distributed, scalable MDS 15, which is a component of the storagesystem 300, can be made up of one or more metadata partitions (84 a-84n). A metadata partition cannot belong to more than one file system andeach file system has at least one partition. It should be noted that afile system is a logical hierarchical representation (“tree”) of, forexample and without limitation, files, directories, and devices on asingle physical server with a specified “root”. Usage quotas apply on afile system basis and not on an individual metadata partition basis.

Each metadata partition (84 a-84 n) is made up of an MDS Server (101a-101 n) and an MDS database (100 a-100 n). Each MDS Server (101 a-101n) includes a Quota Usage Server (20 a-20 n) function and Quota UsageUpdater function (40 a-40 n). Each MDS Database (100 a-100 n) includes aQuota Usage Database portion (30 a-30 n). The terms Quota Usage Serverfunction and Quota Usage Server are equivalent and can be usedinterchangeably. The terms Quota Usage Updater function and Quota UsageUpdater are equivalent and can be used interchangeably. The terms QuotaUsage Database portion and Quota Usage Database are equivalent and canalso be used interchangeably. Together, the Quota Usage Server, QuotaUsage Updater, and Quota Usage Database make up the Quota Usage System10 a-10 n. It should be noted that the Quota Usage Server, Quota UsageUpdater, and Quota Usage Database can be implemented as a functionwithin one or more processes or as individual processes while operatingwithin the spirit and scope of the invention.

The distributed, scalable Storage Service 16, which is a component ofthe storage system 300, can be made up of storage servers 85 a-85 n andstorage devices 87 a-87 n. Each storage server 85 a-85 n can include oneor more storage classes 88 a-88 n. Storage classes provide a level ofabstraction to quotas by assigning a collection of Quality of Service(QoS) attributes to a particular storage class. Thus, instead of quotasbeing viewed in terms of physical bytes, quotas can now be viewed interms of cost. This concept of cost can also be applied to other storagecharacteristics, such as replicating data locally or remotely, storingdata redundantly (using Redundant Arrays of Inexpensive Disks (RAID) orsome other device technology), and so forth. QoS attributes can definestorage device characteristics, for example and without limitation,performance (speed), reliability (redundancy), and accessibility(availability). Therefore, associated with each storage class is thecost of storing the data. The designation of storage classes is providedby way of example only and those of ordinary skill in the art willunderstand that numerous other resources such as network bandwidth, CPUusage, and memory usage may be designated and resource classes can beused to provide a level of abstraction to quotas by assigning acollection of resource-specific QoS to a particular resource class.Similarly, instead of quotas being viewed in terms traditional to theresource, quotas for resources can now be viewed in terms of cost. Adistributed, scalable Quota Enforcement Service 19, which is an optionalcomponent of the storage system 300, can be made up of one or more QuotaAggregation and Enforcement Service nodes 50 a-50 n. Each service nodeaggregates quota usage and quota usage limit information, and initiatesquota enforcement for a single file system, that is, for all thepartitions that make up a file system.

FIG. 1 also shows that Gateway Service 13 communicates with the MDS 15,Storage Service 16, the SMS 17, and the Configuration Database (CDB) 18via network 14. The SMS 17 accesses the CDB 18 as well. Within the MDS15, the Quota Usage Server 20 a-20 n accesses Quota Usage Database 30a-30 n. The MDS server 101 a-101 n, along with the Quota Usage Server 20a-20 n can be a single process on one machine, multiple processes on asingle machine, or multiple processes on multiple machines. In addition,one or more Gateway service nodes 70 a-70 n can access a file system andeach file system can have at least one partition in the presentinvention.

Each MDS 15 manages one or more MDS partitions 84 a-84 n, but each MDSpartition 84 a-84 n is associated with only one MDS 15. An MDS database100 a-100 n for a single file system can contain data for one or more(not shown) metadata partitions 84 a-84 n. A Quota Usage System 10 a-10n handles quota usage information 160 a-160 n, which applies to a filesystem as a whole rather than to metadata partitions 84 a-84 nseparately. However, the quota usage information 160 a-160 n can bemaintained on an individual metadata partition 84 a-84 n basis.

The storage system 300 is illustrated as comprising a distributedGateway Service 13, made up of Gateway Service nodes 70 a-70 n, adistributed Storage Service 16, made up of storage servers 85 a-85 n andstorage devices 87 a-87 n, and a distributed Metadata Service 15, madeup of MDS servers 101 a-101 n and MDS databases 100 a-100 n, but thoseskilled in the relevant art(s) will understand, based on the teachingscontained herein, that fewer or additional, Gateway Service nodes 70a-70 n, storage servers 85 a-85 n, storage devices 87 a-87 n, MDSservers 101 a-101 n and MDS databases 100 a-100 n, as well as otherservices may be removed from, or added to the illustrated storage systemand still be within the spirit and scope of the invention.

It should be noted that the Storage System 300 as shown in FIG. 1includes a distributed Quota Aggregation and Enforcement Service 19.Although quota aggregation and enforcement is a valuable feature, itsinclusion within a system is determined by customer requirements and thepresent invention is not necessarily limited by its inclusion orexclusion.

Looking now to FIG. 2, which is an overview of a method for managingresource usage quotas 200 according to an embodiment of the presentinvention (steps 210-280). The function of managing resource usagequotas (150 in FIG. 1) requires the definition of classes, definition ofusage policies, application of quotas, generation of reports, and thestorage of data by resource class in accordance with quota usage limits.Storage classes are provided for purposes of illustration only, and arenot limiting. Classes can be defined for any type of resource for whicha quota may be desirable. A class adds a level of abstraction to theconcept of usage quotas and has the advantage of assigning a cost to aparticular class. For example, in the context of storage, using classesto define quotas has the advantage of quotas referring to the cost ofstorage instead of referring to, for example, actual storage in physicalbytes that are to be allocated to a user. It should be noted that whenthe customer configures a user for a storage system 300, the customerdefines classes and defines usage policies. It should also be noted thatthe Quota Usage System (10 a-10 n in FIG. 1) interacts with other systemcomponents, such as the SMS (17 in FIG. 1), the Gateway Service (13 inFIG. 1), and the Storage Service (16 in FIG. 1) to implement quotas. Forexample, in the present invention the SMS 17 handles quota definitionsthat the customer defines; the SMS 17 sets quotas and stores usagequotas (150 in FIG. 1) in the CDB 18. During the class-definition phaseof the management of resource usage quotas method, a customer definesthe QoS attributes, which define class characteristics, for example andwithout limitation, performance, reliability, and accessibility, forstorage classes (step 210). The QoS attributes can be very flexible andarbitrary based on customer needs. A customer can then define classes byassigning a Class Identification (ID) and QoS attributes to each definedclass (step 220). The characteristics of a class depend on the QoSattributes assigned to it. As a result of defining QoS attributes (step210) and defining classes (step 220), a cost of using that class ofresource is implicitly assigned (step 235). The assignment of QoSattributes by Class ID in the present invention will be described belowin more detail in connection with FIG. 3.

When at least one class is defined, the management of resource usagequotas method can proceed to the usage-policies-definition phase. Duringthis phase, usage quota policies are defined for a plurality of users(step 240). A usage quota policy helps a customer to automate the quotaassignment process, that is, a customer can define a usage policy thatcan be applied to any number of users. A policy can be defined as a setquotas of one or more storage classes. Any user defined with that policywould have the storage classes associated with the policy assigned tothat user. Usage quota policies automate the quota assignment process.Instead of individually assigning quotas of various storage classes toeach user individually, policies can be used to easily assign quotas toa class of users. For example, Usage Policy A can assign to each userassigned this policy 10 MB of Very Reliable Storage, 20 MB of ReliableStorage, 10 MB of Adequately Reliable Storage and 5 MB of Very HighlyReliable Storage. Usage Policy B can assign to each user assigned thispolicy 20 MB of Reliable Storage and 40 MB of Adequately ReliableStorage. The customer can assign Usage Policy A to Users 1-6, and UsagePolicy B to Users 7-12. A customer typically configures several usersand/or several user groups, that is, a class of users, and for eachselected user or user group assigns selected usage quotas for each classdefined in steps 210 and 220, for example and without limitation,storage class, as needed, or sets a usage policy. The SMS 17 thencreates, in the CDB 18, the quota limits for each user or file systembased on the configuration information, that is, specific usage quotaassignment or policy, provided by a customer. Defining and reportingquotas in the present invention will be described below in more detailin connection with FIG. 4.

When at least one usage policy is defined, the management of resourceusage quotas method can proceed to the application-of-quotas phase. Thisphase is done without operator intervention. During this phase, theQuota Usage system (10 a-10 n on FIG. 1), Gateway Service node (70 a-70n in FIG. 1), SMS (17 in FIG. 1), CDB (18 in FIG. 1), and a QuotaEnforcement Service (19 in FIG. 1) interact to track, aggregate, andenforce quotas.

When quotas are defined for a user or file system in the CDB (18 in FIG.1), the Quota Usage System (10 a-10 n in FIG. 1) can track them (step250). Quotas for a file system or a user may be made up of at least onenumber, but quotas are often a matrix of storage space, the number ofnodes for each storage class, and the sum of all of these. Trackingquotas requires the Quota Usage System to update the informationcontained in the Quota Usage Database (30-30 n in FIG. 1) and to make itavailable when aggregating, enforcing, and reporting quota usage. Eachpartition tracks its own quota usage, but it should be noted that quotasapply per file system. Therefore, quota usages should be aggregated.Tracking quotas in the present invention will be described in moredetail in connection with FIG. 5.

Quota usage information is maintained on an individual metadatapartition basis. Aggregating quota usage information and enforcementallows quota usage information maintained by the Quota Usage System onan individual metadata partition basis to be collected together for anentire file system, that is, for all partitions that make up a filesystem (optional step 260). A Quota Aggregation and Enforcement Service(19 in FIG. 1) can aggregate quota usage information. Aggregating quotasin the present invention will be described in more detail in connectionwith FIG. 6.

In addition, because quotas can be defined, tracked, and enforced byfile owner or an entire file system (that is, one or more metadatapartitions), many different reports relating to quota usage informationcan be generated (step 280). The customer can customize reports andthereby has flexibility in determining the types of reports to begenerated.

Upon successful resource class definition, usage policy definition, andusage quota application (that is, tracking, aggregating, and enforcing),data can be stored accordingly in a Storage Service 16 (made up ofinterconnected Storage Servers 85 a-85 n and Storage devices 87 a-87 nin FIG. 1) by resource class (88 a-88 n in FIG. 1). The resource class(88 a-88 n in FIG. 1) dictates the cost of storing data. For example, acustomer can use a limited number of expensive, high-performance fileservers that hold a “working set” of data, and also have a large amountof inexpensive storage (such as low-performance, inexpensive fileservers, tape robots, jukeboxes with optical disks, etc.) to providestorage capacity for infrequently used data. A class can define how andat what cost the customer wants to store data. It should be noted thatthe migration of data from a storage device is entirely transparent andautomatic (on-demand upon a request to read or write to a file, orasynchronously whenever a file is being migrated to tertiary storage).Also file data stored initially on any given Storage Server (85 a-85 nin FIG. 1) can be migrated later to any other node.

Looking now to FIG. 3, the exemplary assignment of QoS attributes and aClass ID to a class in the present invention will now be described. Inthis example, the class is a storage class and the QoS attributes relateto storage, but the invention is not so limiting. Each storage class 340is assigned QoS attributes 341, Storage Class ID (SCID) 342 andimplicitly a storage cost. The QoS attributes 341 can include individualfile, individual directory, and/or distributed computing systemcharacteristics such as performance, reliability, availability, latency,and so forth. These however, are provided by way of example only andthose of ordinary skill in the art will understand that numerous otherattributes relating to other ways to describe data storage performanceof the class may be designated. Each storage class 340, for example, anadequately reliable class, a reliable class, a very reliable class, ahighly reliable class, and a very highly reliable class can each beassigned a particular set of values for each of the QoS attributes 341as defined for that storage class. For example, storage class“reliable”, assigned Storage Class ID (SCID) 2, has an implicit storagecost of 2×$. The collection of quality of service attributes 141assigned to the “reliable” storage class include: performance of 1000file creations/sec., reliability of RAID1, availability of 1, latency of20 msec., and bandwidth of 10 Mbps.

Looking now to FIG. 4, defining and reporting usage quota policies forusers or a file system in the present invention will now be described.When a customer configures users for a system, for example and withoutlimitation a storage system, the customer assigns a quota for each classto each user (or file system) or sets a usage policy. To make such anassignment, the customer must add a file owner by assigning an ID toeach file owner (step 410), configure a file owner for the system (step420), and must assign a usage quota for each file owner based on systemcapabilities and customer requirements (step 430). When a customerassigns quotas to users or file systems, this information is reported toSMS 17, which handles the processing of the quota definitions. The SMS17 creates storage class usage quota limits based on thecustomer-assigned quotas (step 440) and stores them in the CDB 18 (step450). The SMS 17 then contacts the Quota Usage Server 20 a-20 n toretrieve current quota usage information 160 a-160 n (step 460). Withthis information the SMS 17 can update the information stored in the CDB18 and generate a usage report. The Quota Usage Server retrieves theinformation from the Quota Usage Database 30 a-30 n (step 470), andreturns the updated quota usage information 160 a-160 n to the SMS 17(step 480). The SMS 17 can then include the updated current usageinformation in a usage report (step 490). It should be noted that thegenerated report is based on customer requirements.

Looking now to FIG. 5, a method for quota usage tracking is shown. AGateway Service node 70 a-70 n receives a request to create, delete, ormodify a file (collectively, a file modification request), for exampleand without limitation a request to modify the file length (step 510).The Gateway Service node 70 a-70 n then reads the metadata for the file(step 515) from the MDS 15, or alternatively, from its own cache. TheGateway Service node 70 a-70 n can check whether it has received a quotalimit exceeded notification for a particular file system or user fromthe Quota Aggregation and Enforcement Service 19 (step 520). Thepresence or absence of a notification depends on usage tracking set by acustomer. If a notification is not present, the Gateway Service nodecontinues by executing the relevant user request (step 535). If anotification is present for the particular file system or user, theGateway Service node 70 a-70 n sends a rejection in response to therelevant user request and discontinues processing it (step 530). Ifprocessing is continued from step 525, the Gateway Service node 70 a-70n can send a metadata update, in this example, a change to the filesize, to the MDS 15 (step 535). The MDS Server (101 a-101 n in FIG. 1)updates the record in the MDS Database (100 a-100 n in FIG. 1) for thefile contained in the update request and updates the corresponding usageinformation for the owner identified in the metadata update request(step 540). More particularly, a Quota Usage Updater (40 a-40 n inFIG. 1) of the MDS Server synchronously updates the quota usageinformation (160 a-160 n in FIG. 1) stored in the Quota Usage Database(30 a-30 n in FIG. 1) of the MDS Database (100 a-100 n in FIG. 1) (step545). The Quota Usage Updater 40 a-40 n updates the stored quota usageinformation (160 a-160 n in FIG. 1) using the owner ID. The update,which is based on the update sent from a Gateway Service node, caninclude file owner (in the case of owner change), file storage class,and file size changes, if any. It should be noted that if the user IDcontained in the update does not exist in the Quota Usage Database (30a-30 n in FIG. 1) when the Quota Usage Updater 40 a-40 n receives theupdate, the Quota Usage Updater 40 a-40 n dynamically creates an entryfor the user ID (step 550).

Referring now to FIG. 6, a method for quota usage aggregation andenforcement is shown. Each service node (50 a-50 n in FIG. 1) aggregatesquota usage and quota usage limit information and initiates quotaenforcement for a single file system, that is, for all the partitionsthat make up a file system. Enforcement of usage quotas can be achievedwith a Gateway Service node 70 a-70 n providing the actual enforcementof the quotas, while the Quota Aggregation and Enforcement Service 19provides the necessary notification to the Gateway Service node 70 a-70n to make the enforcement decision. Thus, a Quota Usage System, a QuotaAggregation and Enforcement Service node, and a Gateway Service nodecombine to achieve quota enforcement.

To gather quota limit information, a Quota Usage Aggregation andEnforcement service polls the CDB 18 for quota limits (step 710). Moreparticularly, each Quota Aggregation and Enforcement Service node 50a-50 n polls the CDB 18 for quota limits pertinent to a file system forwhich it is gathering information. This includes quota limit informationabout the file system and the users that can own files in that filesystem. Upon receipt of this information, a Quota Aggregation andEnforcement Service node 50 a-50 n creates a quota table, which includesquota limit information for a file system, and all users and storageclasses associated with that file system for which a quota limit hasbeen set (step 715). Storage classes are defined per user and per filesystem. When a Quota Aggregation and Enforcement Service node 50 a-50 ncreates a quota table, it can periodically poll the Quota Usage Databasein each partition for quota usage information (step 720). The QuotaUsage Database sends quota information to a Quota Usage Aggregation andEnforcement Service node (step 725). It can then add the information itreceives from the Quota Usage Database to the quota table (step 728).The quota table can then contain the quota limit information as well asthe current quota usage information, thereby providing a snapshot of theuse of resources by class for each file system and user. The Quota UsageAggregation and Enforcement Service node 50 a-50 n checks whether aquota limit for a file system, storage class, or user is exceeded ornearly exceeded (step 730). The quota limit can be a hard quota or asoft quota. A hard quota would be a limit that cannot be exceeded underany circumstances. A soft quota, for example and without limitation, canbe exceeded for a predefined period of time with perhaps warningmessages sent to the user. A soft quota is more like a policy thatdetermines behavior when nearing the allowable use of resources. Forexample and without limitation, a soft limit can be made up of threenumbers, a soft quota storage size, a predefined time that specifies howlong a user can be over the soft quota, and a hard quota. The behaviorof an enforcement system when a user is nearing the usage limit can besimple to elaborate depending on customer requirements. For example,once a quota limit is exceeded or nearly exceeded (step 735), the QuotaAggregation and Enforcement Service node 50 a-50 n can send anotification to the Gateway Service nodes 70 a-70 n, which can updatethe relevant file system. The notification can indicate that the quotalimit for the file system, storage class, or user has been exceeded oris about to be exceeded (step 740). It should be further apparent tothose skilled in the relevant art(s) that policies for handling soft orhard quotas can vary widely and still be within the spirit and scope ofthe invention.

Whether the Quota Aggregation and Enforcement Service 19 sends anotification when a limit has been exceeded or some measure before canbe configurable. It should be noted that the Gateway Service node 70a-70 n performs the actual enforcement by rejecting or accepting arequest to create or modify a file from a client.

Although the present invention has been particularly described withreference to the preferred embodiments thereof, it should be readilyapparent to those of ordinary skill in the art that changes andmodifications in the form and details may be made without departing fromthe spirit and scope of the invention. It is intended that the appendedclaims include such changes and modifications. It should be furtherapparent to those skilled in the art that the various embodiments arenot necessarily exclusive, but that features of some embodiments may becombined with features of other embodiments while remaining with thespirit and scope of the invention.

1-13. (canceled)
 14. A method for managing the cost of utilization ofcomputer resources, said method comprising the steps of: a) definingclasses of computer resources based on quality of service attributes theclasses having assigned costs; b) defining computer resource usagepolicies based on said class definitions; c) managing the cost ofutilization of the computer resources by using the computer resourcesaccording to said usage policies; and d) controlling usage of thecomputer resources by particular users based on the assigned costs andusage policies.
 15. The method as defined in claim 14 wherein saidquality of service attributes are selected from a group includingresource performance, resource reliability, resource availability,resource latency, and resource bandwidth.
 16. The method as defined inclaim 14 wherein said step a) further includes assigning each class anidentification designator.
 17. The method as defined in claim 14 whereinsaid step b) further includes the step of assigning usage quotas to eachof said defined classes.
 18. The system as defined in claim 17 whereinsaid usage quotas are hard quotas.
 19. The method as defined in claim 17wherein said usage quotas are soft quotas.
 20. A method for managingcomputer resources, comprising the steps of: a) defining classes ofpersistent computer resources, said classes having assigned costs; b)defining computer resource usage policies; c) applying said usagepolicies to said classes; d) generating reports on the usage of saidclasses; and e) controlling usage of said persistent computer resourcesby particular individuals according to said defined classes inaccordance with said computer resource usage policies and assignedcosts.
 21. (canceled)
 22. The method as defined in claim 20 wherein saidstep a) further includes: i) defining quality of service attributes. 23.The method as defined in claim 22 wherein said service attributes areselected from a group including resource performance resourcereliability, resource availability, resource latency, and resourcebandwidth.
 24. The method as defined in claim 23 wherein each class isassigned a class identification.
 25. The method as defined in claim 20wherein said step b) further includes: i) assigning usage quotas to saiddefined classes.
 26. The method as defined in claim 25 wherein said stepc) further includes: i) tracking, aggregating, and enforcing said usagequotas.
 27. The method as defined in claim 25 wherein said quotas arehard quotas.
 28. The method as defined in claim 27 wherein said hardquotas cannot be exceeded under any circumstances.
 29. The method asdefined in claim 25 wherein said quotas are soft quotas.
 30. The methodas defined in claim 29 wherein said soft quotas may be exceeded for apredetermined period of time.
 31. The method as defined in claim 26wherein said enforcement includes sending notification when a usagequota has been exceeded.
 32. The method as defined in claim 31 furtherincluding rejecting or accepting a request to use a computer resourcewhen a quota has been exceeded.